Project Abstract/Summary This proposal is a NHLBI-RFA (R44) to develop and validate a novel human cell-based diagnostic tool for predicting individual cystic fibrosis (CF) patient responses to drugs that improve the function of mutated forms of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Large- scale in vitro expansion of human nasal epithelial cells is now feasible. The primary cells, when differentiated as air/liquid interface cultures (ALI), recapitulate a patient-specific CFTR phenotype and provide a sensitive and reproducible platform for testing CFTR-directed therapeutics. Transepithelial ion transport is a direct measure of CFTR function and in vitro demonstration of improved function of mutated CFTR has been shown to predict clinical benefit in specific patients. Nasal epithelial cells are collected from CF subjects, cultured, and cryopreserved to generate a bank of cells of known CFTR genotype. Cells are expanded, seeded onto filter supports for ALI culture (up to ~5,000 cultures/subject), differentiated, tested for CFTR expression and activity. The immediate goals of this project are to use the primary HNE cell cultures to: 1) establish reproducibility of inter-patient CFTR- drug response variability, 2) determine if in vitro responses predict long-term in vivo clinical benefit, and 3) identify rare mutations that respond to existing CFTR modulators. The long term goal is to show that this in vitro human cell model predicts individual patient responses to CFTR-directed therapeutics and to develop a diagnostic platform to guide optimization of personalized therapies for all CF patients.